Pressure switches



Nov. 15, 1960 E. E. KUSSMAUL EI'AL PRESSURE SWITCHES Filed Nov. 7, 1958 INVENTORS EDWIN E. KUSSMAUL BYCHARLES E. BURT KENWAY, IFNNFV WITTVP R, HIDRETH ATTORN EYS nited States Patent PRESSURE SWITCHES Edwin E. Kussmaul and Charles E. Burt, Westwood, Mass., assignors to Kelek Company, Norwood, Mass., a corporation of Massachusetts Filed Nov. 7, 1958, Ser. No. 772,574

2 Claims. (Cl. 200--170) The present invention relates to pressure switches and more particularly lto switches of the general type de scribed in the Burt, Kussmaul and McKechnie Patent No. 2,845,512, ldated July 29, 1958, which switches are of high current capacity and are designed to maintain the contact surfaces under considerable pressure when closed.

The principal object of the present invention is to provide improvements in pressure switches of this nature with a view toward maintaining full pressure when closed, providing ease of unlocking and opening when necessary, and positively preventing operation of the pressure applying devices except during the final closing movement of the bl-ade.

With the above and other objects in view as will hereinafter appear, the present invention comprises the pressure switch hereinafter described and particularly defined in the claims.

In the yaccompanying drawings Fig. l is a -plan view of the switch according to the present invention;

Fig. 2 is a side elevation of the switch shown in Fig. l with ythe blades in closed position;

Fig. 3 is a view similar to Fig. 2, but with the blades in open position, some of the parts being shown in section; and

Fig. 4 is a fragmentary view showing the position of the parts when the blades are partly open.

The illustrated embodiment of )the invention comprises a switch body in general similar to that described in the above-mentioned patent, comprising two lengths of hollow square copper tubing shown generally at 6 4and 8 for the pivot and jamb portions respectively. The top walls are cut away in a manner ydescribed in the aboveanentioned patent so that the side walls 10 of the square 6 and the side walls 12 of the square 8 constitute the tixed blades of the switch. The two sections 6 and 8 of the switch body are mounted on a suitable insulating base 14.

The switch has two -movable blades at each side, namely, an outer blade 16 and an inner blade 18. The movable blades on each side are pivoted on a bolt 20 which passes through the side walls 10. The left-hand ends of the movable blades are adapted to embrace the side walls 12 which constitute the fixed blades of the jamb portion of the switch.

A manual operating handle 22 is provided for opening and closing the switch. The handle is mounted for pivotal movement about the axis of the bolt 20, and for that purpose is provided with a split hub 24 internally threaded to receive an externally threaded bushing 2S which is free to rotate on the shank of the bolt. The bushing has a face plate 26 adapted to bear against the inner surface of one of the blades 18. The initial setting of the plate 18 is elected by turning the bushing 25 within the hub until the plate 26 bears against the blade, after which the hub 24 is locked -to the bushing by a screw 28. Connected to the handle are means for ICC Vapplying pressure -to the blades at the pivot end of the switch. To this end the cam arrangement shown in the prior patent is preferably used. The hub is formed at one end with cam surfaces adapted to engage with surfaces 29 on a plate attached to one of the blades 18. Starting from closed position as shown in Figs. 1 and 2, the first opening movement of the handle to the position shown in Fig. 4 causes -a relative rotation lbetween the cams, thereby relieving the outward pressure on the movable blades 18.

Pressure is applied to the blades at the jamb end of the switch by means of a yoke 30 pivoted at 32 to the handle. The yoke is provided with a longitudinally extending Wedging member 34 which passes between two wedge blocks 36 and 38 at the jamb end of the switch. The block 36 is `free on the bolt 44 and the block 38 is provided with a threaded hub 40 to rotate internally within a threaded plate 42 which is initially adjusted to bear against the inner face of the movable blade. The initial pressure is adjusted by turning the plate on the threaded hub 40, after which the plate is secured by Ia set screw in a bracket 43. A bolt 44 passes through the wedge blocks and secures the movable blades in proper relation, without, however, preventing slight lateral motion of the movable blades for the purpose of applying contact pressure. vDuring closing movement of the switch the bolt is accommodated in a vertical slot 46 in each of the fixed blades 16 and 18. The wedge member 34 rides against the inner surface of the block 36 and also rides within an inclined slot 37 in the block 38. Antifriction members shown as rollers 50 are provided for the bearing surfaces between the wedge member 34 and the wedge blocks 36 and 38. It will be seen that upon longitudinal motion of the mem-ber 34, the wedge blocks will be separated, thereby applying pressure to the switch blades. The member 34 undergoes some rotary motion `as well as longitudinal motion during an opening or closing movement, and this rotary motion is used also to turn the wedge block 38. Wedging or pressing action is obtained not only by the interaction of the member 34 in the blocks but also through the rotation of the threaded member 40 within the hub 42.

The wedge member 34 is provided with a longitudinal slot 52 to permit the relative longitudinal movement be tween the wedge member and the blades.

Except for differences in the specific means for applying the Wedging action, the construction thus far described is in general similar to that of the above-mentioned patent.

A fixed cam plate S6 is mounted over .the Wedging cam 29 and is secured in station-ary position by means of a bolt 58 secured to the base 14. The plate 56 has a circular upper surface 57 which is concentric with the bolt 20. The cam plate also has a substantially straight vertical surface 60 immediately forward of the pivot 20.

The yoke 30 has a backwardly projecting portion 62 acting as a cam follower to ride over the surfaces 60 and 57 in a manner to be presently described. Preferably the follower 62 is formed with a lower foot-like part 63 to bottom against a surface 64 of the cam plate when the switch is closed.

When the switch isV closed as indicated in Figs. l and 2, the movable switch blades are wedged against the stationary blades. Under these conditions as shown in Fig. 2, the axes of the bolts 20 and 44 and the axis of the pivot 32 may be all substantially in line, but preferably the axis of the pivot 32 is carried slightly below the axes of the bolts in order to give an irreversible toggle action which resists blowing open of the switch on a short circuit.

Upon lifting the handle there is relative rotary move ment between the handle and the yoke until the position generally shown in Fig. 4 is reached. This releases the wedging actions at the pivot and jamb ends. During this initial motion the foot 63 of the follower 62 has been constrained to Iride up the `vertical surface` 60 of the cam plate.- Upon further motion of the handle about the axis of the bolt k20, the foot 63 rides over the surface 57 of the cam. It will be observed that the triangular relation between the points 20, 32 and` 44 which appears in the intermediate position of Fig. 4 is retained as the follower rides over the circle 57 (Fig. 3).

Positive locking of the switch against unwanted wedg ing action is provided. by the engagement of the foot63 against the cam surface 57 during the complete travel of the blades on their closing movement. lIt will be seen that but for the engagement of the follower with the cam surface it would be possible to eifect a relative rotary movement -between the handle and the yoke 30 `during the first part of the closing movement, thereby causing relative movement between the yoke and the movable blades, which would result in wedging the movable blades before their engagement with the fixed blades. By the provision of the cam follower, however, as shown in Fig. 3, such rotary motion between the handle and yoke cannot occur until the follower has reached the position shown in Fig. 4 where it is clear of the cam surface. At this time the movable blades have been fully seated. Further downward movement of the handle then allows the foot 63 to ride down the vertical surface 60 of the cam (although not necessarily in `actual contact therewith) the foot 63 against the surface 64. All parts are ultimately brought to the condition of Fig. 2. It is during the last part of the downward motion, namely, from the position of Fig. 4 to that of Fig. 2, that relative rotary motion between the handle and yoke is allowed to occur and this motion causes the wedging action by which the pressure is :applied between the movable and fixed blades at both the pivot `and jamb ends of the switch.

Having thus described the invention, we claim:

1. A pressure switch comprising xed and movable blades, a pivot for the movable blades, a handle for operating the movable blades arranged for rotary movement about the pivot axis, wedging means for applying pressure between the movable and xed blades near the end of a closing movement, said wedging means including a yoke member, a pivot for the yoke member on the handle to permit an initial rockin-g of the yoke movement relative to the movable blades upon an opening operation of the switch, a cam member having a curved surface, and a cam follower on the yoke arranged to engage the cam member only after said initial movement, the curved surface of the cam engaging the cam follower during the further movement of the handle to prevent relative movement between the yoke and the movable blades, said pivots and said wedging means being arranged approximately in a straight line when the switch is closed vand in a triangular relation when the follower engages the curved surface of the cam.

2. A pressure switch comprising lixed and movable blades, a pivot for the movable blades, a handle for operating the movable blades arranged for rotary movement about the pivot axis, wedging means for applying pressure between the movable and fixed yblades near the end of a closing movement, said wedging means including a yoke member, a pivot for the yoke member on theV handle, a slotted connection between the yoke member and the movable blades to permit an initial rocking movement of the yoke without opening the blades followed by opening of the blades upon continued movement of the handle, a fixed cam member, and a cam follower on the yoke, the cam member having a curved surface to be engaged by the yoke only after said initial movement rto prevent relative movement between the yoke and the 4movable blades during said engagement of the follower With the curved surface, said pivots and said wedging means being arranged approximately in a straight line when the switch is closed and in a triangular relation when the follower engages the curved surface of the cam.

References Cited in the file of this patent UNITED STATES PATENTS 2,246,072 Scott June 17, 1941 

